The present invention relates to a vehicle axle assembly comprising an axle, means for rotatably mounting a ground engaging wheel at each end of the axle, a fluid power brake mechanism mounted to the axle adjacent each end thereof, each brake mechanism being operative when actuated to restrain rotation of a wheel rotatably mounted at that end of the axle, a valve having a body, means providing a source of pressurized fluid to the body, conduits connecting the body to the brake mechanism at each end of the axle, relay means within the body being operable when actuated to supply fluid pressure from the source to the brake mechanism, a wheel speed sensor mounted at each end of the axle, an annular sintered metal rotor press fitted on a hub rotatably mounted on each end of the axle and supporting the wheel, the rotor having a plurality of circumferentially and equally spaced notches, the notches so disposed on the rotor to angularly sweep by the sensor, the sensor adapted to generate electrical signals indicative of the angular velocity of the rotor and in turn of the hub and the wheel associated therewith, means for modulating the operation of the relay valve mounted in the body comprised of electrical means mounted in the body and electrically connected to the wheel speed sensors.
Most vehicle anti-skid brake control system function in response to electrical signals indicative of the angular velocity of one or more of the vehicle wheels. Generally, these signals are derived from an electromagnetic sensor including a magnet carried by a stationary portion of the vehicle such as the axle housing, and a toothed or notched ring or rotor rotatable with the wheel opposite the magnet. As the teeth or notches of the ring pass the magnetic sensor unit the resulting variations in flux generate a signal, the frequency of which is a function of the angular velocity of the wheel.
To produce the required accuracy of the velocity signal, the sensor unit and rotor must be precisely located with respect to each other and must remain in a preselected relationship even after extended operation in which the components are subjected to road shocks and constant vibration. It is also essential that installation of the components be compatible with mass production techniques. The mounting of the sensor units must also be such that upon reinstallation of a wheel after removal for repair, the parts will automatically be restored to their original operating position.
Wheel speed sensor modules including means permitting automatic adjustment of the magnetic sensor units relative to a rotor are disclosed in U.S. Pat. No. 3,772,548 which issued to R. C. Wroblewski, et. al. on Nov. 13, 1973 and Patent Application Ser. No. 527,609, filed on Nov. 27, 1974 and assigned to the assignee of the present invention. Those modules comprise magnetic sensor units which are movable relative to a supporting frame or housing. An improved sensor module bracket is as set forth in U.S. Pat. Application Ser. No. 621,216 filed Oct. 9, 1975 and entitled "Sensor Module Bracket".
The present invention provides a sintered metal rotor to be used in conjunction with wheel speed sensors as, for example, the above-noted wheel speed sensor to produce the required velocity signal that in turn drives the electromagnetic and electronic mechanisms to control the brakes of a vehicle, particularly in a potential "skid" situation.